1. Field of the Invention
The present invention relates to integrated circuit manufacturing methods.
The method of the present invention more specifically aims at forming, under a layer of a first material, empty areas and/or portions of another material.
2. Discussion of the Related Art
Known ion implantation techniques enable forming buried layers in a substrate by having implanted ions react with the substrate. An example of an ion implantation is the implantation of oxygen O2 in a silicon substrate to form buried silicon oxide layers SiO2.
This implantation technique is however relatively destructive for the upper part of the substrate. Further, it does not enable forming a buried layer of any type of material. Further, the thickness of the buried layer is difficult to control.
Another known buried layer forming technique is that implemented for example upon forming of devices of SON (silicon on nothing) type. After the epitaxial growth of a silicon/germanium layer followed by a silicon layer, one or several portions of the silicon layer are etched to be able to remove, by etching, the underlying silicon/germanium layer. A dielectric or conductive layer is then deposited under the silicon layer by filling the space previously taken up by the silicon/germanium layer.
Once the layer has been deposited, no known technique enables removing chosen portions of the dielectric or conductive layer. A disadvantage of this technique thus is that the deposited layer necessarily has a shape identical to that of the silicon/germanium layer.